[vsnet-alert 843] CVC 134 (DV UMa Superhump Period, V795 Cyg)

[Tonny Vanmunster <tvanmuns@innet.be>]

BELGIAN ASTRONOMICAL SOCIETY V.V.S. -  Working Group Variable Stars
Cataclysmic Variables Circular No.134                1997, April 14
Ed.: T. Vanmunster, Walhostraat 1A, 3401 Landen, BELGIUM
     Internet: tvanmuns@innet.be                  TEL. 32-11-831504
     CBA Belgium Web Page : http://vsnet.astro.columbia.edu/~cba/be
===================================================================

DV UMa [UGSU, 15.4v - 20.6v]
============================

In a recent VSNET message, Tonny Vanmunster, CBA Belgium Observatory
announced the discovery of superhumps in this system, hence
classifying it as a UGSU type dwarf nova : "I performed unfiltered 
time series photometry on DV UMa at CBA Belgium Observatory last night 
(April 9/10, 1997), during 4.8 hours. The resulting light curve shows 
three eclipses and very prominent superhumps. These observations thus 
establish DV UMa as a new member of the UGSU-type dwarf novae."

Joe Patterson, CBA (Columbia University), NY communicates following
precise data on the superhump period : "I received a lot of data on 
DV UMa, coming from CBA Denmark (Lasse Jensen), CBA West (Dave
Harvey) and CBA Belgium (Tonny Vanmunster), and the star now shows 
very large superhumps at nu = 11.22 +- 0.05 c/d.  The superhump
amplitude is about 0.35 mag.  One very large run on JD 548 has an 
obvious signal at 23.52 c/d, which I take to be the first harmonic of 
nu-orb, a la AL Com and WZ Sge."

In CVC 133, we listed a mid-eclipse ephemeris for DV UMa, published by
Taichi Kato, consisting of two possible alternatives. An analysis
by T. Vanmunster of a set of DV UMa time series photometry data, 
obtained on April 9/10 at the Center for Backyard Astrophysics of 
Dave Skillman (CBA East) and CBA Belgium, clearly indicates that
the best fit ephemeris is the first one : 

  Min.HJD = 2446854.7487 + 0.085852614 E     (1),

The observed eclipses fit within the 0.002 day error mentioned by 
Taichi Kato [CVC 133]. 


V795 Cyg [UGSS, 13.4p - <17.9:p]
================================

The outburst of V795 Cyg, mentioned in CVC 132, has received some 
further coverage.

As to the dwarf nova subtype status of V795 Cyg, we still have to
conclude that this object most likely is of an SS Cyg subtype.
We performed time-series CCD photometry on V795 Cyg at CBA
Belgium Observatory on three successive nights (Apr 7/8, Apr 8/9
and Apr 9/10) for a total of 7.1 hours, but on each occasion the
light curve failed to reveal superhumps.
     

Tonny Vanmunster

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